in public key cryptography there should be two key called private key and public key
private key kept in secret and public key put in public
in public key cryptography the its should be easy to encrypt and decrypt the files using keys
either of these keys can used to encrypt the file and other key can be used to decrypt the file
generation of these keys should be easy
it should be unfeasible to decrypt the cipher text using same key which is used to encrypt the file .
by knowing the public key the opponent cant determine the private key and it should be unfeasible
but computing power needed for public key cryptography is higher than private key cryptography